Elastomeric compounds incorporating silicon-treated carbon blacks

ABSTRACT

Disclosed are elastomeric compounds including an elastomer and a silicon-treated carbon black, and optionally including a coupling agent. The elastomeric compound exhibits poorer abrasion resistance, lower hysterisis at high temperature and comparable or increased hysterisis at low temperature compared to an elastomer containing an untreated carbon black. Elastomeric compounds incorporating an elastomer and an oxidized, silicon-treated carbon black are also disclosed. Also disclosed are methods for preparing elastomers compounded with the treated carbon black.

This application is a Continuation of prior application Ser. No.08/876,903 filed Jun. 17, 1997, which is a Divisional of Ser. No.08/446,141 filed May 22, 1995, now U.S. Pat. No. 5,830,930.

RELATED APPLICATIONS

This application is related to the following applications identified bytitle and attorneys' docket number, filed on even date herewith, forwhich serial numbers have not yet been accorded: Mineral Binders ColoredWith Silicon-Containing Carbon Black (0639/0A991); Elastomeric CompoundsIncorporating Partially Coated Carbon Blacks (0639/0B060); andElastomeric Compounds Incorporating Silicon-Treated Carbon Blacks andCoupling Agents (0639/0B059). The disclosure of each of the foregoingapplications is hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to novel elastomeric compounds exhibitingimproved hysterisis properties. More particularly, the invention relatesto novel elastomeric compounds incorporating silicon-treated carbonblacks.

BACKGROUND OF THE INVENTION

Carbon blacks are widely used as pigments, fillers and reinforcingagents in the compounding and preparation of rubber and otherelastomeric compounds. Carbon blacks are particularly useful asreinforcing agents in the preparation of elastomeric compounds used inthe manufacture of tires.

Carbon blacks are generally produced in a furnace-type reactor bypyrolyzing a hydrocarbon feedstock with hot combustion gases to producecombustion products containing particulate carbon black. Carbon blackexists in the form of aggregates. The aggregates, in turn are formed ofcarbon black particles. However, carbon black particles do not generallyexist independently of the carbon black aggregate. Carbon blacks aregenerally characterized on the basis of analytical properties,including, but not limited to particle size and specific surface area;aggregate size, shape, and distribution; and chemical and physicalproperties of the surface. The properties of carbon blacks areanalytically determined by tests known to the art. For example, nitrogenadsorption surface area (measured by ASTM test procedure D3037--MethodA) and cetyl-trimethyl ammonium bromide adsorption value (CTAB)(measured by ASTM test procedure D3765 [09.01]), are measures ofspecific surface area. Dibutylphthalate absorption of the crushed (CDBP)(measured by ASTM test procedure D3493-86) and uncrushed (DBP) carbonblack (measured by ASTM test procedure D2414-93), relates to theaggregate structure. The bound rubber value relates to the surfaceactivity of the carbon black. The properties of a given carbon blackdepend upon the conditions of manufacture and may be modified, e.g., byaltering temperature, pressure, feedstock, residence time, quenchtemperature, throughput, and other parameters.

It is generally desirable in the production of tires to employ carbonblack-containing compounds when constructing the tread and otherportions of the tire. For example, a suitable tread compound will employan elastomer compounded to provide high abrasion resistance and goodhysterisis balance at different temperatures. A tire having highabrasion resistance is desirable because abrasion resistance isproportional to tire life. The physical properties of the carbon blackdirectly influence the abrasion resistance and hysterisis of the treadcompound. Generally, a carbon black with a high surface area and smallparticle size will impart a high abrasion resistance and high hysterisisto the tread compound. Carbon black loading also affects the abrasionresistance of the elastomeric compounds. Abrasion resistance increaseswith increased loading, at least to an optimum point, beyond whichabrasion resistance actually decreases.

The hysterisis of an elastomeric compound relates to the energydissipated under cyclic deformation. In other words, the hysterisis ofan elastomeric composition relates to the difference between the energyapplied to deform the elastomeric composition and the energy released asthe elastomeric composition recovers to its initial undeformed state.Hysterisis is characterized by a loss tangent, tan δ, which is a ratioof the loss modulus to the storage modulus (that is, viscous modulus toelastic modulus). Tires made with a tire tread compound having a lowerhysterisis measured at higher temperatures, such as 40° C. or higher,will have reduced rolling resistance, which in turn, results in reducedfuel consumption by the vehicle using the tire. At the same time, a tiretread with a higher hysterisis value measured at low temperature, suchas 0° C. or lower, will result in a tire with high wet traction and skidresistance which will increase driving safety. Thus, a tire treadcompound demonstrating low hysterisis at high temperatures and highhysterisis at low temperatures can be said to have a good hysterisisbalance.

There are many other applications where it is useful to provide anelastomer exhibiting a good hysterisis balance but where the abrasionresistance is not an important factor. Such applications include but arenot limited to tire components such as undertread, wedge compounds,sidewall, carcass, apex, bead filler and wire skim; engine mounts; andbase compounds used in industrial drive and automotive belts.

Silica is also used as a reinforcing agent (or filler) for elastomers.However, using silica alone as a reinforcing agent for elastomer leadsto poor performance compared to the results obtained with carbon blackalone as the reinforcing agent. It is theorized that strongfiller-filler interaction and poor filler-elastomer interaction accountsfor the poor performance of silica. The silica-elastomer interaction canbe improved by chemically bonding the two with a chemical couplingagent, such as bis (3-triethoxysilylpropyl) tetrasulfane, commerciallyavailable as Si-69 from Degussa AG, Germany. Coupling agents such asSi-69 create a chemical linkage between the elastomer and the silica,thereby coupling the silica to the elastomer.

When the silica is chemically coupled to the elastomer, certainperformance characteristics of the resulting elastomeric composition areenhanced. When incorporated into vehicle tires, such elastomericcompounds provide improved hysterisis balance. However, elastomercompounds containing silica as the primary reinforcing agent exhibit lowthermal conductivity, high electrical resistivity, high density and poorprocessibility.

When carbon black alone is used as a reinforcing agent in elastomericcompositions, it does not chemically couple to the elastomer but thecarbon black surface provides many sites for interacting with theelastomer. While the use of a coupling agent with carbon black mightprovide some improvement in performance to an elastomeric composition,the improvement is not comparable to that obtained when using a couplingagent with silica.

It is an object of the present invention to provide novel elastomericcompounds exhibiting improved hysterisis balance. It is another objectto provide an elastomeric compound incorporating silicon-treated carbonblacks. It is yet another object of the present invention to provide anelastomeric compound incorporating silicon-treated carbon blacks,wherein the carbon black may be efficiently coupled to the elastomerwith a coupling agent. Such a carbon black may be employed for example,in tire compounds, industrial rubber products and other rubber goods. Itis yet another object to provide a reinforcing agent which includes sucha carbon black and a coupling agent. Other objects of the presentinvention will become apparent from the following description andclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a portion of one type of carbon blackreactor which may be used to produce the treated carbon blacks of thepresent invention.

FIG. 2 is a graph demonstrating the results of a bound rubber testcarried out on elastomeric compositions of the present invention.

FIGS. 3a, 3b and 3c are graphs demonstrating hysterisis values measuredat different temperatures and strains on elastomeric compositions of thepresent invention.

FIGS. 4a-4d are photomicrographs comparing carbon blacks useful in thepresent invention and prior art carbon blacks.

SUMMARY OF THE INVENTION

The present invention is directed to an elastomeric compound includingan elastomer and a silicon-treated carbon black, and optionallyincluding a coupling agent. The silicon-treated carbon black imparts tothe elastomer poorer abrasion resistance, lower hysterisis at hightemperature and comparable or increased hysterisis at low temperaturecompared to an untreated carbon black. Elastomeric compoundsincorporating an elastomer and an oxidized, silicon-treated carbon blackare also disclosed. Also disclosed are methods for preparing elastomericcompounds with the silicon-treated carbon blacks.

DETAILED DESCRIPTION OF THE INVENTION

The present inventors have discovered that elastomeric compounds havingdesirable hysterisis and other properties may be obtained by compoundingan elastomer with a silicon-treated carbon black. In the silicon-treatedcarbon black a silicon-containing species, including but not limited to,oxides and carbides of silicon, may be distributed through at least aportion of the carbon black aggregate as an intrinsic part of the carbonblack.

In an elastomeric compound including an elastomer and a silicon-treatedcarbon black, the silicon-treated carbon black imparts to the elastomerpoorer abrasion resistance, comparable or higher loss tangent at lowtemperature and a lower loss tangent at high temperature, compared to anuntreated carbon black.

Silicon-treated carbon black aggregates do not represent a mixture ofdiscrete carbon black aggregates and discrete silica aggregates. Rather,the silicon-treated carbon black aggregates of the present inventioninclude at least one silicon-containing region either at the surface ofor within the carbon black aggregate.

When the silicon-treated carbon black is examined under STEM-EDX, thesilicon signal corresponding to the silicon-containing species is foundto be present in individual carbon black aggregates. By comparison, forexample, in a physical mixture of silica and carbon black, STEM-EDXexamination reveals distinctly separate silica and carbon blackaggregates.

The silicon-treated carbon blacks may be obtained by manufacturing thecarbon black in the presence of volatizable silicon-containingcompounds. Such carbon blacks are preferably produced in a modular or"staged, " furnace carbon black reactor as depicted in FIG. 1. Thefurnace carbon black reactor has a combustion zone 1, with a zone ofconverging diameter 2; a feedstock injection zone with restricteddiameter 3; and a reaction zone 4.

To produce carbon blacks with the reactor described above, hotcombustion cases are generated in combustion zone 1 by contacting aliquid or gaseous fuel with a suitable oxidant stream such as air,oxygen, or mixtures of air and oxygen. Among the fuels suitable for usein contacting the oxidant stream in combustion zone 1, to generate thehot combustion gases, are included any readily combustible gas, vapor orliquid streams such as natural gas, hydrogen, methane, acetylene,alcohols, or kerosene. It is generally preferred, however, to use fuelshaving a high content of carbon-containing components and in particular,hydrocarbons. The ratio of air to fuel varies with the type of fuelutilized. When natural gas is used to produce the carbon blacks of thepresent invention, the ratio of air to fuel may be from about 10:1 toabout 1000:1. To facilitate the generation of hot combustion gases, theoxidant stream may be pre-heated.

The hot combustion gas stream flows downstream from zones 1 and 2 intozones 3 and 4. The direction of the flow of hot combustion gases isshown in FIG. 1 by the arrow. Carbon black feedstock, 6, is introducedat point 7 into the feedstock injection zone 3. The feedstock isinjected into the gas stream through nozzles designed for optimaldistribution of the oil in the gas stream. Such nozzles may be eithersingle or bi-fluid. Bi-fluid nozzles may use steam or air to atomize thefuel. Single-fluid nozzles may be pressure atomized or the feedstock canbe directly injected into the gas-stream. In the latter instance,atomization occurs by the force of the gas-stream.

Carbon blacks can be produced by the pyrolysis or partial combustion ofany liquid or gaseous hydrocarbon. Preferred carbon black feedstocksinclude petroleum refinery sources such as decanted oils from catalyticcracking operations, as well as the by-products from coking operationsand olefin manufacturing operations.

The mixture of carbon black-yielding feedstock and hot combustion gasesflows downstream through zone 3 and 4. In the reaction zone portion ofthe reactor, the feedstock is pyrolyzed to carbon black. The reaction isarrested in the quench zone of the reactor. Quench 8 is locateddownstream of the reaction zone and sprays a quenching fluid, generallywater, into the stream of newly formed carbon black particles. Thequench serves to cool the carbon black particles and to reduce thetemperature of the gaseous stream and decrease the reaction rate. Q isthe distance from the beginning of reaction zone 4 to quench point 8,and will vary according to the position of the quench. Optionally,quenching may be staged, or take place at several points in the reactor.

After the carbon black is quenched, the cooled gases and carbon blackpass downstream into any conventional cooling and separating meanswhereby the carbon black is recovered. The separation of the carbonblack from the gas stream is readily accomplished by conventional meanssuch as a precipitator, cyclone separator, bag filter or other meansknown to those skilled in the art. After the carbon black has beenseparated from the gas stream, it is optionally subjected to apelletization step.

The silicon treated carbon blacks of the present invention may be madeby introducing a volatilizable silicon containing compound into thecarbon black reactor at a point upstream of the quench zone. Usefulvolatilizable compounds include any compound, which is volatilizable atcarbon black reactor temperatures. Examples include, but are not limitedto silicates such as tetraethoxy orthosilicate (TEOS) and tetramethoxyorthosilicate, silanes such as, tetrachloro silane, and trichloromethylsilane; and volatile silicone polymers such asoctamethylcyclotetrasiloxane (OMTS). The flow rate of the volatilizablecompound will determine the weight percent of silicon in the treatedcarbon black. The weight percent of silicon in the treated carbon blackshould range from about 0.1% to 25%, and preferably about 0.5% to about10%, and most preferably about 2% to about 6%.

The volatilizable compound may be premixed with the carbon black-formingfeedstock and introduced with the feedstock into the reaction zone.Alternatively, the volatilizable compound may be introduced to thereaction zone separately from the feedstock injection point. Suchintroduction may be upstream or downstream from the feedstock injectionpoint, provided the volatilizable compound is introduced upstream fromthe quench zone. For example, referring to FIG. 1, the volatilizablecompound may be introduced to zone Q at point 12 or any other point inthe zone. Upon volatilization and exposure to high temperatures in thereactor, the compound decomposes, and reacts with other species in thereaction zone, yielding silicon treated carbon black, such that thesilicon, or silicon containing species, becomes an intrinsic part of thecarbon black.

As discussed in further detail below, if the volatilizable compound isintroduced substantially simultaneously with the feedstock, thesilicon-treated regions are distributed throughout at least a portion ofthe carbon black aggregate.

In a second embodiment of the present invention, the volatilizablecompound is introduced to the reaction zone at a point after carbonblack formation has commenced but before the reaction stream has beensubjected to the quench. In this embodiment, silicon-treated carbonblack aggregates are obtained in which a silicon containing species ispresent primarily at or near the surface of the carbon black aggregate.

It has been found by the present inventors that the elastomericcompounds incorporating a treated carbon black may be additionallycompounded with one or more coupling agents to further enhance theproperties of the elastomeric compound. Coupling agents useful forcoupling silica or carbon black to an elastomer, are expected to beuseful with the silicon-treated carbon blacks. Useful coupling agentsinclude, but are not limited to, silane coupling agents such asbis(3-triethoxysilylpropyl)tetrasulfane (Si-69),3-thiocyanatopropyl-triethoxy silane (Si-264, from Degussa AG, Germany),γ-mercaptopropyI-trimethoxy silane (A189, from Union Carbide Corp.,Danbury, Conn.); zirconate coupling agents, such as zirconiumdineoalkanolatodi(3-mercapto) propionato-O (NZ 66A, from KenrichPetrochemicals, Inc., of Bayonne, N.J.); titanate coupling agents; nitrocoupling agents such asN,N'-bis(2-methyl-2-nitropropyl)-1,6-diaminohexane (Sumifine 1162, fromSumitomo Chemical Co., Japan); and mixtures of any of the foregoing. Thecoupling agents may be provided as a mixture with a suitable carrier,for example X50-S which is a mixture of Si-69 and N330 carbon black,available from Degussa AG.

The silicon-treated carbon black incorporated in the elastomericcompound of the present invention may be oxidized and/or combined with acoupling agent. Suitable oxidizing agents include, but are not limitedto, nitric acid and ozone. Coupling agents which may be used with theoxidized carbon blacks include, but are not limited to, any of thecoupling agents set forth above.

The silicon-treated carbon blacks of the present invention may have anorganic group attached, as disclosed in U.S. patent application Ser. No.356,459, filed Dec. 15, 1994, and entitled "EPDM, HNBR and Butyl RubberCompositions Containing Carbon Black Products", hereby incorporated byreference herein. Preferred organic groups include aromatic sulfides,represented by the formulas Ar--S_(n) --Ar' or Ar--S_(n) --Ar", whereinAr and Ar' are independently arylene groups, Ar" is an aryl and n is 1to 8.

Another set of organic groups which may be attached to the carbon blackare organic groups substituted with an ionic or an ionizable group as afunctional group, as disclosed in U.S. patent application Ser. No.356,660, filed Dec. 15, 1994 and entitled "Reaction of Carbon Black withDiazonium Salts, Resultant Carbon Black Products and Their Uses", herebyincorporated by reference herein.

The elastomeric compounds of the present invention may be prepared fromthe treated carbon blacks by compounding with any elastomer includingthose useful for compounding a carbon black. Any suitable elastomer maybe compounded with the treated carbon blacks to provide the elastomericcompounds of the present invention. Such elastomers include, but are notlimited to, homo- or co-polymers of 1,3 butadiene, styrene, isoprene,isobutylene, 2,3-dimethyl-1,3-butadiene, acrylonitrile, ethylene, andpropylene. Preferably, the elastomer has a glass transition temperature(Tg) as measured by differential scanning colorimetry (DSC) ranging fromabout -120° C. to about 0° C. Examples include, but are not limited,styrene-butadiene rubber (SBR), natural rubber, polybutadiene, andpolyisoprene. Blends of any of the foregoing may also be used.

The elastomeric compositions may include one or more curing agents suchas, for example, sulfur, sulfur donors, activators, accelerators,peroxides, and other systems used to effect vulcanization of theelastomer composition.

The resultant elastomeric compounds containing treated carbon black andoptionally containing one or more coupling agents may be used forvarious elastomeric products such as treads for vehicle tires,industrial rubber products, seals, timing belts, power transmissionbelting, and other rubber goods. When utilized in tires, the elastomericcompounds may be used in the tread or in other components of the tire,for example, the carcass and sidewall.

Tread compounds produced with the present elastomeric compoundsincorporating a silicon-treated carbon black but without a couplingagent, provide improved dynamic hysterisis characteristics. However,elastomeric compounds incorporating a silicon-treated carbon black and acoupling agent demonstrate further improved characteristics when testedfor dynamic hysterisis at different temperatures and resistance toabrasion. Therefore, a tire incorporating a tread compound manufacturedwith an elastomeric compound of the present invention, incorporatingboth a silicon-treated carbon black and a coupling agent willdemonstrate even lower rolling resistance, good wet traction and betterwear resistance when compared with a tire made with a tread compoundincorporating the treated carbon black but lacking the coupling agent.

The following examples illustrate the invention without limitation.

EXAMPLES Example 1

Silicon-treated carbon blacks according to the present invention wereprepared using a pilot scale reactor generally as described above, andas depicted in FIG. 1 and having the dimensions set forth below: D₁ =4inches, D₂ =2 inches, D₃ =5 inches, L₁ =4 inches, L₂ =5 inches, L₃ =7inches, L₄ =1 foot and Q=4.5 feet. The reaction conditions set forth inTable 1 below, were employed.

These conditions result in the formation of a carbon black identified bythe ASTM designation N234. A commercially available example of N234 isVulcan® 7H from Cabot Corporation, Boston, Mass. These conditions werealtered by adding a volatilizable silicon-containing compound into thereactor, to obtain a silicon-treated carbon black. The flow rate of thevolatilizable compound was adjusted to alter the weight percent ofsilicon in the treated carbon black. The weight percent of silicon inthe treated carbon black was determined by the ashing test, conductedaccording to ASTM procedure D-1506.

One such new treated carbon black was made by injecting anorgano-silicon compound, namely octamethyl-cyclotetrasiloxane (OMTS),into the hydrocarbon feedstock. This compound is sold as "D4" by DowCorning Corporation, Midland, Mich. The resultant silicon-treated carbonblack is identified herein as OMTS-CB. A different silicon-treatedcarbon black (TEOS-CB) was prepared by introducing a secondsilicon-containing volatilizable compound, tetraethoxy silane, (sold asTEOS, by Huls America, Piscataway, N.J.), into the hydrocarbonfeedstock.

Since changes in reactor temperature are known to alter the surface areaof the carbon black, and reactor temperature is very sensitive to thetotal flow rate of the feedstock in the injection zone (zone 3 in FIG.1), the feedstock flow rate was adjusted downward to approximatelycompensate for the introduction of the volatilizable silicon-containingcompound, such that a constant reactor temperature was maintained. Thisresults in an approximately constant external surface area (as measuredby t area) for the resultant carbon blacks. All other conditions weremaintained as necessary for manufacturing N234 carbon black. A structurecontrol additive (potassium acetate solution) was injected into thefeedstock to maintain the specification structure of the N234 carbonblack. The flow rate of this additive was maintained constant in makingthe silicon-treated carbon blacks described throughout the followingexamples.

The external surface area (t-area) was measured following the samplepreparation and measurement procedure described in ASTM D3037--Method Afor Nitrogen surface area. For this measurement, the nitrogen adsorptionisotherm was extended up to 0.55 relative pressure. The relativepressure is the pressure (P) divided by the saturation pressure (P₀)(the pressure at which the nitrogen condenses). The adsorption layerthickness (t₁) was then calculated using the relation: ##EQU1##

The volume (V) of nitrogen adsorbed was then plotted against t₁. Astraight line was then fitted through the data points for t₁ valuesbetween 3.9 and 6.2 Angstroms. The t-area was then obtained from theslope of this line as follows:

    t-area, m.sup.2 /gm=15.47×slope

                  TABLE 1                                                         ______________________________________                                                    Carbon Black                                                      Conditions    N234      TEOS-CB   OMTS-CB                                     ______________________________________                                        Air Rate, kscfh                                                                             12.8      12.8      12.8                                          Gas Rate, kscfh 0.94 0.94 0.94                                                feedstock rate, lbs/hr 166 139 155                                            Si compound rate, lbs/hr 0 16 5                                             ______________________________________                                    

The resultant carbon blacks were analyzed for surface area and siliconcontent. These values are set forth in Table 2 below:

                  TABLE 2                                                         ______________________________________                                                     Carbon Black                                                     Properties     N234     TEOS-CB   OMTS-CB                                     ______________________________________                                        % Silicon in Carbon Black                                                                    0.02     2.85      2.08                                          DBP, cc/100 g 125.0 114.0 115.0                                               CDBP, cc/100 g 101.5 104.1 103.5                                              t-Area, m.sup.2 /g 117.0 121.0 121.0                                          N.sub.2 area, m.sup.2 /g 120.4 136.0 133.0                                  ______________________________________                                    

Example 2

A scanning transmission electron microscope (STEM) coupled to an energydispersive X-ray analyzer, was used to further characterize thesilicon-treated carbon black. The following Table 3 compares N234,OMTS-CB (prepared according to Example 1) and N234 to which 3.7% byweight silica (L90, sold as CAB-O-SIL® L90, by Cabot Corporation,Boston, Mass.) was added to form a mixture. As described below, the STEMsystem may be used to examine an individual aggregate of carbon blackfor elemental composition. A physical mixture of carbon black and silicawill result in the identification of silica aggregates which show mostlysilicon signal and little or background carbon signal. Thus, whenmultiple aggregates are examined in a mixture, some of the aggregateswill show a high Si/C signal ratio, corresponding to aggregates ofsilica.

Five mg of carbon black was dispersed into 20 ml of chloroform andsubjected to ultrasonic energy using a probe sonicator (W-385 HeatSystems Ultra Sonicator). A 2 ml aliquot was then dispersed into 15 mlof chloroform using a probe sonicator for three minutes. The resultingdispersion was placed on a 200 mesh nickel grid with aluminum substrate.The grid was then placed under a Fisons HB501 Scanning TransmissionElectron Microscope (Fisons, West Sussex, England) equipped with anOxford Link AN10000 Energy Dispersive X-ray Analyzer (Oxford Link,Concord, Mass.). Initially the grid was scanned for potential silicaaggregates at low magnification (less than 200,000×). This was done bysearching for aggregates that had a Si/C count ratio greater than unity.After this initial scan, typically thirty aggregates were selected fordetailed analysis at higher magnification (from between 200,000× and2,000,000×). The selected aggregates included all of the aggregateswhich contained Si/C count ratios greater than unity, as identified bythe initial scan. The highest ratios of Si/C counts thus determined areset forth in Table 3 for N234, OMTS-CB and a mixture of N234 and silica.

                  TABLE 3                                                         ______________________________________                                        Ratio of Si/C Signal Measured with STEM                                                     % Si in Mod-                                                                             Highest Ratio of                                       ified Sample Si/C Counts per Aggregate                                      ______________________________________                                        N234          0          0.02                                                   OMTS-CB 3.28 0.27                                                             N234 + 3.7% silica (L90) 1.7 49                                             ______________________________________                                    

Thus, a well dispersed mixture of carbon black and silica having thesame silicon content as the OMTS-CB shows 180 times higher peak Si/Ccounts. This data shows that the OMTS-CB carbon black is not a simplephysical mixture of silica and carbon black, but rather that the siliconis a part of the intrinsic chemical nature of the carbon black.

Example 3

HF Treatment

Hydrofluoric acid (HF) is able to dissolve silicon compounds but doesnot react with carbon. Thus, if either a conventional (untreated) carbonblack or a mixture of silica and carbon black is treated with HF, thesurface and surface area of the carbon black will remain unchanged,because it is unaffected by the dissolution of the silicon compoundsremoved from the mixture. However, if silicon containing species aredistributed throughout at least a portion, including the surface, of thecarbon black aggregate, the surface area will markedly increase asmicropores are formed as the silicon compound is dissolved out of thecarbon black structure.

Five grams of the carbon black to be tested were extracted with 100 mlof 10% v/v hydrofluoric acid for 1 hour. The silicon content andnitrogen surface area were measured before and after the HF treatment.The results are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                        HF Treatment                                                                          % Si Before                                                                             % Si After HF                                                                            N.sub.2 SA Before                                                                     N.sub.2 SA After                           HF treatment Treatment HF treatment HF treatment                            ______________________________________                                        N234    0.02      0.05       123     123                                        OMTS-CB 3.3 0.3 138 180                                                     ______________________________________                                    

Photomicrographs were taken of the carbon black samples before and afterHF treatment. The photomicrographs are shown in FIGS. 4a-4d. Thesephotographs show that the silicon-treated carbon blacks have a roughersurface, consistent with increased microporosity after the HF treatment,compared to the untreated carbon black.

Example 3A

Another silicon-treated carbon black was made by injecting TEOS into thereaction zone of the reactor immediately (one foot) downstream from thehydrocarbon feedstock injection plane, as indicated at injection point12 in FIG. 1. All other reaction conditions were maintained as requiredfor manufacturing N234 black, as described in Example 1. The TEOS flowrate was adjusted to 17.6 lbs per hour.

The resultant black was analyzed for silicon content and surface area,before and after HF extraction as described in Example 3. The resultsare described in Table 4A.

                  TABLE 4A                                                        ______________________________________                                        manufactured by injection of TEOS into reaction zone                                         % Si N.sub.2 Area                                              ______________________________________                                        Before HF        2.27   127.7                                                   After HF 0.04 125.8                                                         ______________________________________                                    

Thus, no increase in N₂ surface area was seen after HF extraction of theTEOS-CB'. Analysis of the aggregates by the STEM procedure described inExample 2 also showed silicon to be present in the aggregates and not asindependent silica entities. These results show that in this case thesilicon-containing species of the silicon-treated carbon blacks areprimarily located near the surface.

Example 4

Preparation of Elastomeric Compositions

The carbon blacks of the previous Examples were used to make elastomericcompounds. Elastomeric compositions incorporating the silicon-treatedcarbon blacks discussed above, were prepared using the followingelastomers: solution SBR (Duradene 715 and Cariflex S-1215, fromFirestone Synthetic Rubber & Latex Co., Akron, Ohio), functionalizedsolution SBR (NS 114 and NS 116 from Nippon Zeon Co., SL 574 and TO589from Japan Synthetic Rubber Co.), emulsion SBR (SBR 1500, from CopolymerRubber & Chemicals, Corp., Baton Rouge, La.), and natural rubber (SMR5,from Malaysia).

The elastomeric compositions were prepared according to the followingformulation:

                  TABLE 5                                                         ______________________________________                                        Ingredient     Parts by weight                                                ______________________________________                                        elastomer      100                                                              carbon black 50                                                               zinc oxide 3                                                                  stearic acid 2                                                                Flexzone 7P ®  1                                                          Durax ® 1.25                                                              Captax ® 0.2                                                              sulfur 1.75                                                                   Si-69 (optional) 3 or 4                                                     ______________________________________                                    

Flexzone 7P®, N-(1,3-dimethyl butyl)-N'-phenyl-p-phenylene diamine, isan anti-oxidant available from Uniroyal Chemical Co., Middlebury, Conn.Durax®, N-cyclohexane-2-benzothiazole sulphenamide, is an acceleratoravailable from R. T. Vanderbilt Co., of Norwalk, Conn., and Captax®,2-mercaptobenzothiazole, is an accelerator available from R. T.Vanderbilt Co.

The elastomeric compounds were prepared using a two-stage mixingprocedure. The internal mixer used for preparing the compounds was aPlasti-Corder EPL-V (obtained from C. W. Brabender, South Hackensack,N.J.) equipped with a cam-type mixing head (capacity 600 ml). In thefirst stage, the mixer was set at 80° C., and the rotor speed was set at60 rpm. After the mixer was conditioned to 100° C. by heating thechamber with a dummy mixture, the elastomer was loaded and masticatedfor 1 minute. Carbon black, pre-blended with zinc oxide (obtained fromNew Jersey Zinc Co., New Jersey), and optionally a coupling agent, wasthen added. After three minutes, stearic acid (obtained from EmeryChemicals, Cincinnati, Ohio) and anti-oxidant were added. Mixing wascontinued for an additional two minutes. The stage 1 masterbatch wasthen dumped from the mixer at five minutes total. This was then passedthrough an open mill (four inch, two-roll mill, obtained from C. W.Brabender, South Hackensack, N.J.) three times and stored at roomtemperature for two hours.

In the second stage, the mixing chamber temperature was set to 80° C.and the rotor speed was set to 35 rpm. After the mixer was conditionedthe masterbatch from stage one was loaded and mixed for one minute. Thecurative package (including sulfur, Durax and Captax) was then added.The material was dumped from the mixer at two minutes and passed throughthe open mill three times.

Batches of the compounds were prepared as described for the carbonblacks in the previous Examples. The same grade of conventional carbonblack was used as a control. For each carbon black, two batches wereprepared. The first batch was made using Si-69 as the coupling agent.The second batch was made without a coupling agent. After mixing, eachof the elastomeric compositions was cured at 145° C. to an optimum curestate according to measurements made with a Monsanto ODR Rheometer.

Example 5

Bound Rubber Test

The bound rubber content of an elastomeric compound incorporating carbonblack can be taken as a measure of the surface activity of the carbonblack. The higher the bound rubber content, the higher the surfaceactivity of the carbon black. Bound rubber was determined by extractionof an elastomeric compound with toluene at room temperature. The boundrubber is the elastomer remaining after extraction by the solvent. Theelastomer used was solution SBR (SSBR) Duradene 715 without a couplingagent, as described above in Example 4.

As seen in FIG. 2, the bound rubber was determined for a series ofblends of silica and carbon black, which serve as a reference againstwhich to compare the bound rubber of the silicon-treated carbon black.The results of the bound rubber measurements for the two sets ofcompounds are plotted against their equivalent silica content in FIG. 2.For the treated carbon blacks, the equivalent silica content is atheoretical value calculated from the total silicon as measured byashing. It is seen that silicon-treated carbon blacks yield a higherbound rubber than their conventional counterparts. This suggests thatthe treated carbon black surface is relatively more active. Moreover, asshown in FIG. 2, the bound rubber content of treated carbon black-filledcompounds lie well above the reference line generated from the blends ofcarbon black and silica. This confirms that the treated carbon black isnot a physical mixture of silica and carbon black.

Example 6

Dynamic Hysterisis and Abrasion Resistance

The dynamic hysterisis and abrasion resistance rates were measured forthe elastomeric compositions produced according to Example 4 above.

Abrasion resistance was determined using an abrader, which is based on aLambourn-type machine as described in U.S. Pat. No. 4,995,197, herebyincorporated by reference. The tests were carried out at 14% slip. Thepercentage slip is determined based on the relative velocities of asample wheel and a grindstone wheel. The abrasion resistance index iscalculated from the mass loss of the elastomeric compound. Dynamicproperties were determined using a Rheometrics Dynamic Spectrometer II(RDS II, Rheometrics, Inc., N.J.) with strain sweep. The measurementswere made at 0 and 70° C. with strain sweeps over a range of doublestrain amplitude (DSA) from 0.2 to 120%. The maximum tan δ values on thestrain sweep curves were taken for comparing the hysterisis amongelastomeric compounds as can be seen in FIGS. 3a and 3b. Alternatively,hysterisis measurements were made by means of temperature sweeps at aDSA of 5% and a frequency of 10 Hz. The temperature range was from -60°C. to 100° C., as seen in FIG.

                  TABLE 6                                                         ______________________________________                                        Dynamic Hysterisis Data                                                                           tan δ                                                                            tan δ                                                                           abrasion at                                Si-69 at 0° C. at 70° C. 14% slip                             ______________________________________                                        SSBR Composition.sup.a                                                          N234 0 0.400 0.189 100                                                        N234 3 0.429 0.170 103.5                                                      OMTS-CB 0 0.391 0.175 84.4                                                    OMTS-CB 3 0.435 0.152 110.5                                                   TEOS-CB 0 0.400 0.167 78.1                                                    TEOS-CB 3 0.433 0.142 97.2                                                  ______________________________________                                         .sup.a Duradene 715; two stage mixing.                                   

As seen in Table 6 above, tan δ at 70° C. values were reduced by 7%, tanδ at 0° C. values reduced by 2.3% and the wear resistance was reduced by15%, for the SSBR samples when OMTS-CB was substituted for N234.However, when the Si-69 coupling agent was incorporated into thecomposition, the wear resistance for the OMTS-CB sample improved to 110%of the value for N234. The tan δ at 70° C. values decreased by 19.6%compared to N234 without coupling agent and 10.5% compared to N234 withcoupling agent. The tan δ at 0° C. values increased by 11% when thecoupling agent was added to the OMTS-CB, compared to OMTS-CB withoutcoupling agent. Similarly, for TEOS-CB, the tan δ at 70° C. value isreduced by 11.6%, the tan δ at 0° C. value is unchanged and the wear isreduced by 21.9%. When compounded with the coupling agent, the tan δ at70° C. value is reduced by 24.9%, the tan δ at 0° C. value is increasedby 8.3% and the wear decreased by only 2.8%.

It was determined that employing the treated carbon blacks and anelastomer in an elastomeric composition of the present inventiongenerally resulted in poor abrasion resistance, compared to anelastomeric composition including the same elastomer and N234 carbonblack. However, as seen in Table 6, when Si-69 coupling agent wasincorporated into the composition, abrasion resistance returned toapproximately the same values as obtained with untreated carbon black.

As used herein, "untreated carbon black" means a carbon black preparedby a process similar to that used to prepare the corresponding treatedblack, but without the volatizable silicon compound and by makingsuitable adjustments to the process conditions to achieve a carbon blackwith an external surface area approximately equal to that of the treatedblack.

Example 6A

The dynamic hysterisis and abrasion properties of a black made byfollowing the procedure of Example 3A (and containing 1.91% Si) weremeasured as in Example 6. As seen in Table 6A below, tan δ at 70° C.values were reduced by 14%, tan δ at 0° C. values were reduced by 6% andthe wear resistance was reduced by 22%, for the SSBR samples whenTEOS-CB' was substituted for N234. However, when Si69 coupling agent wasincorporated into the composition, the wear resistance for the TEOS-CBsample improved to 108% of the value for N234. The tan δ at 70° C.values decreased by 18% compared to N234 without coupling agent and 7%compared to N234 with coupling agent. The tan δ at 0° C. valuesdecreased by only 1.5% when the coupling agent was added to TEOS-CB',compared to N234 with coupling agent.

                  TABLE 6A                                                        ______________________________________                                        Dynamic Hysterisis Data                                                                                           Abrasion                                    Si 69 tan δ@0° C. tan δ@70° C. @14% Slip          ______________________________________                                        SSBR                                                                            Composition.sup.a                                                             N234 0 0.428 0.184 100                                                        N234 4 0.394 0.162 94                                                         TEOS-CB' 0 0.402 0.158 78                                                     TEOS-CB' 4 0.388 0.151 108                                                  ______________________________________                                         .sup.a Cariflex S1215; two stage mixing                                  

Example 7

Improvement in Hysterisis by Three Stage Compounding

The beneficial properties obtained using the treated carbon blacks withthe elastomeric compounds of the present invention may be furtherenhanced by using an additional mixing stage during the compoundingprocess. The procedure for two stage mixing used in the previouscompounding examples, is described above in Example 4.

For three stage mixing, the stage 1 mixer was set at 80° C. and 60 rpm.After conditioning to 100° C. by heating the chamber with a dummymixture, the elastomer was introduced to the mixer at 100° C. andmasticated for one minute. The carbon black was added to the elastomerand mixing continued for an additional three minutes. In some cases, acoupling agent was also added with the carbon black, at a rate of 3 to 4parts per hundred of elastomer. The stage 1 masterbatch was then dumpedand passed through an open mill three times and stored at roomtemperature for 2 hours. The second stage chamber temperature was alsoset at 80° C. and 60 rpm. After conditioning to 100° C., the masterbatchwas introduced to the mixer, masticated for one minute, and theantioxidant was then added. At four minutes or when a temperature of160° C. is reached, the stage 2 masterbatch was dumped and passedthrough the open mill 3 times and stored at room temperature for 2hours. The third stage chamber temperature was set at 80° C. and 35 rpm.The masterbatch from stage 2 was then added to the mixer and masticatedfor 1 minute. The curing package was then added and the stage 3 materialwas dumped at 2 minutes and passed through an open mill 3 times.

Table 7 below compares hysterisis and abrasion characteristics forelastomers compounded with TEOS-CB using two and three stage mixing. Ascan be seen from the Table, three stage mixing results in higher tan δat 0° C. and lower tan δ at 70° C.

                  TABLE 7                                                         ______________________________________                                        Dynamic Hysterisis Data - 2 Stage v. 3 Stage Mixing                                                   tan δ                                                                          tan δ                                                                           abrasion at                              Carbon Black Si-69 at 0° C. at 70° C. 14% slip                ______________________________________                                        Duradene 715                                                                    Two Stage Mixing                                                              N234 0 0.458 0.189 100                                                        N234 3 0.439 0.170 103.5                                                      TEOS-CB 0 0.434 0.150 78.1                                                    TEOS-CB 3 0.436 0.131 97.2                                                    Duradene 715                                                                  Three Stage Mixing                                                            N234 0 0.471 0.165 100                                                        N234 3 0.456 0.146 98.4                                                       TEOS-CB 0 0.446 0.139 57.6                                                    TEOS-CB 3 0.461 0.113 101.8                                                 ______________________________________                                    

Example 8

Oxidized Carbon Black

In another aspect of the present invention, it was determined by thepresent inventors that oxidation of the silicon-treated carbon black canlead to elastomeric compositions with enhanced hysterisis. For a blackmade using the conditions of Table 1, but with OMTS as the volatilizablesilicon-containing compound, and 2.74% silicon in the final black, theimprovement obtained with oxidation is illustrated in the followingTable. The hysteresis performance with the oxidized black is furtherenhanced by incorporating a coupling agent into the elastomericcompound.

The oxidized carbon black was prepared by treating the black with nitricacid. A small stainless steel drum was loaded with carbon black androtated. During rotation a 65% nitric acid solution is sprayed onto thecarbon black, until 15 parts per hundred carbon black had been added.After a soak period of 5 minutes, the drum was heated to about 80° C. toinitiate the oxidation reaction. During the oxidation reaction, thetemperature increased to about 100-120° C. This temperature was helduntil the reaction was completed. The treated black was then heated to200° C. to remove residual acid. The treated black was then driedovernight at 115° C. in a vacuum oven. Table 8 below compares hysterisischaracteristics for elastomers compounded with OMTS-CB and oxidizedOMTS-CB, with and without a coupling agent.

                  TABLE 8                                                         ______________________________________                                        Dynamic Hysterisis Data - oxidized, treated carbon black                                                   tan δ                                                                         tan δ                                  Carbon Black Si-69 at 0° C. at 70° C.                         ______________________________________                                        Duradene 715 - 2 stage                                                          N234 0 0.513 0.186                                                            N234 3 0.463 0.176                                                            OMTS-CB 0 0.501 0.166                                                         OMTS-CB 3 0.467 0.135                                                         oxidized OMTS-CB 0 0.487 0.154                                                oxidized OMTS-CB 3 0.467 0.133                                              ______________________________________                                    

Example 9

Hysterisis and Abrasion Resistance for a Variety of Elastomers

Hysterisis and abrasion resistance was compared for elastomericcompounds prepared with treated carbon blacks compounded with differentelastomers, compounded with and without a coupling agent. Conventionalcarbon black was used as a control. The results are set forth in theTable 9 below.

These data show hysterisis improvement for all five elastomer systemstested. For example, the tan δ at 70° C. is reduced by between 10.5 and38.3% without a coupling agent, and by between 11.7 and 28.2% with acoupling agent, compared to the corresponding control.

It can also be seen that in all cases abrasion resistance for thetreated carbon black compound compared to the untreated controldecreases when no coupling agent is used. Abrasion resistance issubstantially improved when the coupling agent is used. It can also beseen that the hysterisis balance is improved with treated carbon black(with or without coupling agent), compared to control carbon black.

                  TABLE 9                                                         ______________________________________                                        Hysterisis and Abrasion Resistance - 3 Stage Mixing                                                                    wear at                                Carbon Black Si-69 tan δ at 0° C. tan δ at 70°                                              C. 14%slip                          ______________________________________                                        Solution SBR 116/NS                                                             114 -80/20 blend                                                              N234 0 0.689 0.151 100.0                                                      N234 3 0.750 0.131 123.1                                                      TEOS-CB 0 0.721 0.115 86.3                                                    TEOS-CB 3 0.751 0.094 115.4                                                   Solution SBR SL 574                                                           N234 0 0.286 0.118 100.0                                                      N234 3 0.260 0.108 96.4                                                       TEOS-CB 0 0.246 0.101 58.0                                                    TEOS-CB 3 0.258 0.093 86.8                                                    Solution SBR PAT589                                                           N234 0 0.676 0.190 100.0                                                      N234 3 0.686 0.182 99.1                                                       TEOS-CB 0 0.698 0.170 82.4                                                    TEOS-CB 3 0.726 0.150 134.2                                                   Emulsion SBR 1500                                                             N234 0 0.299 0.176 100.0                                                      N234 3 0.285 0.137 87.9                                                       TEOS-CB 0 0.280 0.156 60.1                                                    TEOS-CB 3 0.270 0.121 88.1                                                    Natural Rubber SMR 5                                                          N234 0 0.253 0.128 100.0                                                      N234 3 0.202 0.088 85.8                                                       TEOS-CB 0 0.190 0.079 60.9                                                    TEOS-CB 3 0.173 0.069 88.6                                                  ______________________________________                                    

All patents, patent applications, test methods, and publicationsmentioned herein are incorporated by reference.

Many variations of the present invention will suggest themselves tothose skilled in the art in light of the above detailed disclosure. Forexample, the compositions of the present invention may include otherreinforcing agents, other fillers, oil extenders, antidegradants, andthe like. All such modifications are within the full intended scope ofthe claims.

What is claimed is:
 1. An elastomeric compound comprising a) anelastomer and b) an aggregate comprising a carbon phase and asilicon-containing species phase, wherein said aggregate has anincreased microporosity after hydrofluoric acid treatment, compared tocarbon black.
 2. The elastomeric compound of claim 1, wherein saidsilicon-containing species phase exists as regions primarily at thesurface of the aggregate.
 3. The elastomeric compound of claim 1,wherein said silicon-containing species phase exists as regionsdistributed throughout the aggregate.
 4. The elastomeric compound ofclaim 1, wherein said aggregate is oxidized.
 5. The elastomeric compoundof claim 1, wherein said elastomer is selected from the group consistingof solution SBR, natural rubber, functional solution SBR, emulsion SBR,polybutadiene, polyisoprene, and blends of any of the foregoing.
 6. Theelastomeric compound of claim 1, wherein said silicon-containing speciesphase comprises between about 0.1% and about 25% elemental silicon, byweight of the aggregate.
 7. The elastomeric compound of claim 6, whereinsaid silicon-containing species phase comprises between about 0.5% andabout 10% elemental silicon, by weight of the aggregate.
 8. Theelastomeric compound of claim 7, wherein said silicon-containing speciesphase comprises between about 2% and about 6% elemental silicon, byweight of the aggregate.
 9. A method for improving the hysterisis of anelastomeric compound comprising compounding an elastomer with anaggregate comprising a carbon phase and a silicon-containing speciesphase, wherein said aggregate has an increased microporosity afterhydrofluoric acid treatment, compared to carbon black.
 10. The method ofclaim 9, wherein said silicon-containing species phase exists as regionsprimarily at the surface of the aggregate.
 11. The method of claim 9,wherein said silicon-containing species phase exists as regionsdistributed throughout the aggregate.
 12. The method of claim 9, whereinsaid aggregate is oxidized.
 13. The method of claim 9, wherein saidelastomer is selected from the group consisting of solution SBR, naturalrubber, functional solution SBR, emulsion SBR, polybutadiene,polyisoprene, and blends of any of the foregoing.
 14. The method ofclaim 9, wherein said silicon-containing species phase comprises betweenabout 0.1% and about 20% silicon, by weight of the aggregate.
 15. Themethod of claim 14, wherein said silicon-containing species phasecomprises between about 0.5% and about 10% elemental silicon, by weightof the aggregate.
 16. The method of claim 15, wherein saidsilicon-containing species phase comprises between about 2% and about 6%elemental silicon, by weight of the aggregate.
 17. An aggregatecomprising a carbon phase and a silicon-containing species phase,wherein said aggregate has an increased microporosity after hydrofluoricacid treatment, compared to carbon black.
 18. The aggregate of claim 17,wherein said silicon-containing species phase exists as regionsprimarily at the surface of the aggregate.
 19. The aggregate of claim17, wherein said silicon-containing species phase exists as regionsdistributed throughout the aggregate.
 20. The aggregate of claim 17,wherein said aggregate is oxidized.
 21. The aggregate of claim 17,wherein said silicon-containing species phase comprises between about0.1% and about 25% elemental silicon, by weight of the aggregate. 22.The aggregate of claim 21, wherein said silicon-containing species phasecomprises between about 0.5% and about 10% elemental silicon, by weightof the aggregate.
 23. The aggregate of claim 22, wherein saidsilicon-containing species phase comprises between about 2% and about 6%elemental silicon, by weight of the aggregate.
 24. A method for reducingrolling resistance of a tire comprising introducing an elastomericcompound comprising an elastomer and an aggregate, wherein saidaggregate comprises a carbon phase and a silicon-containing speciesphase, to a tire compound in an amount effective to reduce said rollingresistance.
 25. The method of claim 24, wherein said aggregate impartsto the elastomer poorer abrasion resistance, comparable or higher losstangent at low temperature and a lower loss tangent at high temperature,compared to carbon black.
 26. The method of claim 24, wherein saidsilicon-containing species phase exists as regions primarily at thesurface of the aggregate.
 27. The method of claim 24, wherein saidsilicon-containing species phase exists as regions distributedthroughout the aggregate.
 28. The method of claim 24, wherein saidaggregate is oxidized.
 29. The method of claim 24, wherein saidelastomer is selected from the group consisting of solution SBR, naturalrubber, functional solution SBR, emulsion SBR, polybutadiene,polyisoprene, and blends of any of the foregoing.
 30. The method ofclaim 24, wherein said silicon-containing species phase comprisesbetween about 0.1% and about 25% elemental silicon, by weight of theaggregate.
 31. The method of claim 30, wherein said silicon-containingspecies phase comprises between about 0.5% and about 10% elementalsilicon, by weight of the aggregate.
 32. The method of claim 31, whereinsaid silicon-containing species phase comprises between about 2% andabout 6% elemental silicon, by weight of the aggregate.
 33. The methodof claim 24, wherein said tire compound is a tread compound.
 34. Themethod of claim 24, further comprising introducing a coupling agent tosaid tire compound in an amount effective to reduce said rollingresistance.
 35. A method for reducing vehicle fuel consumptioncomprising introducing an elastomeric compound comprising an elastomerand an aggregate, wherein said aggregate comprises a carbon phase and asilicon-containing species phase, to a tire compound in an amounteffective to reduce said vehicle fuel consumption.
 36. The method ofclaim 35, wherein said aggregate imparts to the elastomer poorerabrasion resistance, comparable or higher loss tangent at lowtemperature and a lower loss tangent at high temperature, compared tocarbon black.
 37. The method of claim 35, wherein saidsilicon-containing species phase exists as regions primarily at thesurface of the aggregate.
 38. The method of claim 35, wherein saidsilicon-containing species phase exists as regions distributedthroughout the aggregate.
 39. The method of claim 35, wherein saidaggregate is oxidized.
 40. The method of claim 35, wherein saidelastomer is selected from the group consisting of solution SBR, naturalrubber, functional solution SBR, emulsion SBR, polybutadiene,polyisoprene, and blends of any of the foregoing.
 41. The method ofclaim 35, wherein said silicon-containing species phase comprisesbetween about 0.1% and about 25% elemental silicon, by weight of theaggregate.
 42. The method of claim 41, wherein said silicon-containingspecies phase comprises between about 0.5% and about 10% elementalsilicon, by weight of the aggregate.
 43. The method of claim 42, whereinsaid silicon-containing species phase comprises between about 2% andabout 6% elemental silicon, by weight of the aggregate.
 44. The methodof claim 35, wherein said tire compound is a tread compound.
 45. Themethod of claim 35, further comprising introducing a coupling agent tosaid tire compound in an amount effective to reduce said vehicle fuelconsumption.
 46. A method for increasing tire life comprisingintroducing an elastomeric compound comprising an elastomer and anaggregate, wherein said aggregate comprises a carbon phase and asilicon-containing species phase, to a tire compound in an amounteffective to increase said tire life.
 47. The method of claim 46,wherein said aggregate imparts to the elastomer poorer abrasionresistance, comparable or higher loss tangent at low temperature and alower loss tangent at high temperature, compared to carbon black. 48.The method of claim 46, wherein said silicon-containing species phaseexists as regions primarily at the surface of the aggregate.
 49. Themethod of claim 46, wherein said silicon-containing species phase existsas regions distributed throughout the aggregate.
 50. The method of claim46, wherein said aggregate is oxidized.
 51. The method of claim 46,wherein said elastomer is selected from the group consisting of solutionSBR, natural rubber, functional solution SBR, emulsion SBR,polybutadiene, polyisoprene, and blends of any of the foregoing.
 52. Themethod of claim 46, wherein said silicon-containing species phasecomprises between about 0.1% and about 25% elemental silicon, by weightof the aggregate.
 53. The method of claim 52, wherein saidsilicon-containing species phase comprises between about 0.5% and about10% elemental silicon, by weight of the aggregate.
 54. The method ofclaim 53, wherein said silicon-containing species phase comprisesbetween about 2% and about 6% elemental silicon, by weight of theaggregate.
 55. The method of claim 46, wherein said tire compound is atread compound.
 56. The method of claim 46, further comprisingintroducing a coupling agent to said tire compound in an amounteffective to increase said tire life.